Aspirin for primary prevention of myocardial infarction: what is the evidence?

Aspirin has been advocated as a primary prevention measure for myocardial infarction (MI) for more than 2 decades. While several meta-analyses have supported this view, others have differed. All these analyses have focused on data from 6 major clinical trials.

We have provided a detailed analysis of the methods used in the individual trials (n = 6) included in the published meta-analyses.

The major limitations of the meta-analyses relate to inclusion of heterogeneous trials characterized by widely differing study cohorts, absence of true control groups, lack of identification of silent MIs, failure to specify type of stroke, and inadequate information on management of conventional cardiac risk factors such as hypertension and hyperlipidemia. These issues preclude meaningful conclusions on the effects of aspirin in primary prevention of MI.

This analysis does not support a general recommendation for the use of aspirin for primary prevention of MI and also suggests that effective management of risk factors in accordance with current guidelines may attenuate any potential benefit from aspirin with respect to MI. However, there may be a modest benefit in postmenopausal women with respect to stroke.